Diagnostics and testing 4.4L (Discovery 3)

Inspection and verification

1. Check the validity of the customer's complaint.

2. Visually inspect for obvious mechanical problems.

Mechanical factors	Electrical factors
Exhaust Gas Recirculation (EGR) Pipes Ventilation hoses Positive crankcase ventilation valve Fuel level Fuel contamination/fuel brand/fuel quality Throttle body	Fuse box 5 in the battery fuse box Loose or corroded electrical connectors Exhaust Gas Recirculation (EGR) Valve Engine Control Module (ECM)

3. If an obvious cause for the problem you identified or the customer described is found, correct it before proceeding with further actions. (if possible).

4. Use the approved diagnostic system or scan tool to retrieve all diagnostic trouble codes (DTCs) before referring to the symptom chart or DTC index.

Clear all DTCs after troubleshooting.

Table of signs of malfunction

NOTE: For a more complete troubleshooting chart, refer to Section 303-14, Electronic Engine Management System, in the Service Manual.

Sign of malfunction	Possible reason	Operation
Difficulty starting at cold start	Battery Crankshaft Position Sensor (CKP) Exhaust Gas Recirculation (EGR) valve stuck open Fuel system Fuel Evaporative Canister Purge Valve	Battery information, crankshaft position sensor, fuel system and purge valve tests are provided in the relevant sections of the workshop manual. Check the EGR valve. Refer to the guided diagnostic program on the approved diagnostic system.
Engine stalls shortly after starting	Disconnection/reduction of ventilation system capacity ECM relay MAF sensor Ignition system Clogged air filter Air leak Fuel lines	Check the engine breather hoses, PCV, etc. Check the operation of the ECM relay. Information on MAF sensor, ignition system, intake system information and fuel line tests are provided in the appropriate sections of the service manual.
Poor throttle response	APP sensor failure TP sensors ECT sensor MAF sensor Gearbox failure Activating the traction control system Air leak Disconnection/reduction of ventilation system capacity	For information on checking the APP, TP, ECT, MAF, intake system and transmission information, refer to the appropriate sections of the service manual. Check the ventilation hoses, PCV, etc.

DTC Index

NOTE: Generic scan tools cannot read the codes listed or can only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7-digit code to identify the fault. (the last 2 digits provide additional information readable by a manufacturer approved diagnostic system).

NOTE: For a complete listing of ECM DTCs, refer to Section 303-14, Electronic Engine Control System, in the service manual.

DTC	Description	Possible reason	Operation
P040100	Insufficient flow registered in the exhaust gas recirculation system A	EGR pipe blockage EGR valve is incorrectly installed or loose EGR valve stuck closed/clogged EGR valve malfunction	Check the EGR lines. Check the EGR valve installation, refer to the relevant section of the workshop manual. Refer to the guided diagnostic routine for this code on the approved diagnostic system.
P048900	Low voltage in the EGR control circuit	EGR valve power supply circuit: high resistance EGR valve power supply circuit: short circuit electrical circuit to ground	Refer to the guided diagnostic program for this code on the approved diagnostic system.
P049000	High voltage in the EGR control circuit	EGR valve activation circuit: short circuit to +battery	Refer to the guided diagnostic program for this code on the approved diagnostic system.